Impact pulverization plus-additives in the production of activated carbon from coal



Dec; 9, 1969 E. T. oLsoN 3,483,134

S ADDITIVES IN THE PRODUCTION OF IMPACT PULVERIZATION PLU ACTIVATEDCARBON FROM COAL 2 Sheets-Sheet 1 Filed Aug. l5. 1966 shown-JOU .vmbo20mm mm m mollo mz ,M m fd@ z W ruauum Dec. 9, 1969 E. 'r. oLsoN3,483,134

IMPACT PULVERIZATION PLUS ADDITIVES IN THE PRODUCTION OF ACTIVATEDCARBON FROM COAL Filed Aug. l5, 1966 2 Sheets-Sheet 2 EYS United StatesPatent O IMPACT PULVERIZATION PLUS-ADDITIVES lN THE PRODUCTION OFACTIVATED CARBON FROM COAL Edgar T. Olson, Marmora, NJ., assignor toKingsford Company, Louisville, Ky., a corporation of Illinois Filed Aug.15, 1966, Ser. No. 572,363 Int. Cl. C01b 31/12 U.S. Cl. 252-421 15Claims ABSTRACT OF THE DISCLOSURE To make activated carbon from brightbanded bituminous coal, by pulverizing under impact of a particular sizerange, introducing a required quantity of an organic additive which willat least partially vaporize at a tempearture of between 200 F. and thetempearture of heat treating, regulating the moisture content to between2.5 and 11% on the dry weight of the coal, molding into briquettes at aspecified pressure, heat treating the briquettes at a temperaturebetween 250 F. and 800 F. and not in excess of the temperature ofagglomeration of the coal, breaking down the briquettes into granulesand activating the carbon granules. The reaction may be exolthermic.

The present invention relates to processes and apparatus for making hardactivated carbon black of the type which can be repeatedly reactivatedand reused.

In summary, the raw material is bright banded bituminous coal, which inthe preferred embodiment has an analysis by weight as follows:

Volatile Between 28 and 46% most desirably between 39 and 42%.

Fixed carbon Between 49 and 71%, most desirably between 54 and 58%.

Ash Between 1 and 15%, preferably between l and 5%, most desirablybetween 3 and 4%.

The bituminous coal is pulverized under impact to build up a reactionpotential in the coal, and reduce it to the following size range:

At least 60% by weight through 200 mesh, and preferably at least 85% byweight through 200 mesh;

At least 25% by weight through 325 mesh, and preferably at least 60% byweight through 325 mesh.

The coal is mixed with between l and by Weight of the dry coal, andpreferably 2 to 3%, ofk an organic additive which will vaporize at atemperature between 220 F. and the temperature of heat treating, say 800F. The organic additive is most desirably of the type which will reactwith the coal exothermically, such as a cereal or seed, an aldehyde oran amino or ammonium compound. The additive may, however, be a compoundwhich favors azeotropic distillation such as an alcohol, a ketone or anester. The additive may be a halogenated hydrocarbon. The additive mayalso be a multi-ring cyclic hydrocarbon. The moisture content of thecoal is adjusted to bring it within 2.5 and 11% on the dry Weight of the3,483,134 Patented Dec. 9, 1969 "ice Where the volatile in the coal isbelow 38% by weight,

in excess of 10,000 p.s.i.

The molded coal is then heat treated at a temperature between 250 F. and800 F. and not in excess of the temperature of agglomeration of thecoal, for a time of at least four hours, preferably at least five hours.Prior to or after heat treating the briquettes are broken down intogranules, then the carbon granules are activated.

A purpose of the invention is to produce superior activation of carbonas evidenced by the fact that the carbon shows activation propertieseven before activation.

A further purpose is to control the size of pores in activated carbon inorder to give the carbon special properties.

A further purpose is to control the surface chemistry of activatedcarbon and particularly the extent of cross linkage and the extent offree valences.

A further purpose is to produce an activated carbon of higher density,having greater adsorption capacity per cubic foot and thus moreefficiently using the space requirements in adsorption towers and thelike.

A further purpose is to provide an activated carbon which will undergoregeneration more times, With less abrasion loss than comparableproducts now available, by reason of greater hardness and greaterdensity.

A further purpose is to produce a superior activated carbon from areadily available low cost raw material, that is, bituminous coal,sub-bituminous coal, or semibituminous coal, the latter being includedin the term bituminous coal when used herein.

A further purpose is to produce, from a low grade raw material such asbituminous coal, an activated carbon having properties similar tococoanut shell activated carbon. f

A further purpose is to convert mechanical energy used in pulverizingbituminous coal to chemical energy which is capable of assisting andpromoting the reaction between the coal and the additives.

Further purposes appear in the specification and in the claims.

In the drawings I have chosen to illustrate one only of the numerousembodiments of equipment which may be used to carry out the process ofthe invention, the forms shown being illustrated diagrammatically.

FIGURE 1 is a diagrammatic iloW sheet of the first portion of theprocess of the invention, illustrating apparatus which may be employed.

FIGURE 2 is a diagrammatic flow sheet of the latter part of the processaccording to the invention, illustrating suitable apparatus.

In the prior art a wide variety of raw materials are used to produceactivated carbon for the purposes of making adsorbants for use in liquidphase and in gaseous phase systems. While in many cases relativelyexpensive raw materials such as cocoanut shell carbon and fruit pitcarbon have been used, limited success has also been achieved in makingactivated carbons from more available materials such as bituminous coal.

atsaist and mixed with a binder'such as tar, compressed into briquettesand then heat treated to produce activated carbon. See Morrell U.S.Patents 1,968,846 and 1,968,847; 2,008,144, 2,008,145, and 2,088,146;and Barrett U.S. Patent 3,021,287.

The present invention is concerned with an improved process andapparatus for manufacture of activated carbon from bituminous coal.

One of the important effects achieved is that the activated carbon ofthe invention has superior activation and even shows activationproperties before it is activated. In accordance with the invention thesize and character of the pores in the activated carbon are subject tocontrol, and also the surface chemistry of the carbon is controlled,particularly in respect to cross linkage and free valences.

One of the unusual features is that the carbon of the invention hasgreater density for a given adsorption capacity, thus more effectivelyutilizing the space in adsorption towers and the like, and being harderand denser, is capable of undergoing many regenerations without seriousloss.

A further feature of the invention which is of great importance is thatthe pulverizing converts mechanical energy into chemical energy byimpacting the particles and this energy is partially or wholly liberatedduring the heat treatment. In fact, with certain additives the reactionis exothermic, once it is started at a suitable temperature range.

In making activated carbon according to the invention it is important tostart with a bright banded bituminous coal. It Will be remembered thatbituminous coals are characterized by several different petrographicsubstituents. Vitrain is the constituent of lowest ash content. When itis nearly pure it may have less than 0.5% ash. It behaves as a plastic.

Fusain in bituminous coal is essentially mineral charcoal. It has awoody structure and its ash content may be in the range of 15 to 20% byweight.

Clarain is a translucent material made up of such ingredients as spores,algae, and exines (outer shells of spores and the like). It is somewhatsimilar to vitrain but has higher contents of nitrogen and sulphur andis also relatively low in ash (1 to 2% by Weight).

Durain is a constituent formed from organic matter such as twigs, bark,leaves and moss, and forms the bulk constituent of dull coal. It has anash content in the range of to 15% by weight.

Bituminous coals, as well known in the art, are classified into brightbanded coals which consist mainly of vitrain and clarain and are of lowash content and dull coals which consist mainly of durain and fusain andare of high ash content.

In general the bituminous coal after removal of slate which has thelowest ash content has the highest content of vitrain and clarain.

A large part of the high ash bituminous coals consists of so-calledslate. This is a deposit laid down by water including clay, mineralfragments, iron-bearing materials, bark and the like.

The ash in fusain is primarily lime and sulphates. The ash in vitrainand clarain is primarily alkali, alumina and sulphates. The ash indurain is chiey alumina and silica.

A good bright banded bituminous coal as mined may contain up to of ashby weight. This material is beneficiated by any well known means toremove slate, rock and part of the clay. The coal is rst crushed to anominal size of 1A inch. One mechanism for accomplishing this is ashaking table, of which a well known acceptable type is made Iby Sutton,Steele and Steele. The beneiiciation reduces the ash content to lessthan 15% and preferably less than 5%, and separates debris which willoften contain 40% of ash and will be suitable for burning under theboiler to generate steam for the activator.

The beneiated bright banded pituniinous coal which is used as a rawmaterial in the invention will have an analysisV asfollows ona`moisture-f`ree or dry basis by weight:

Volatile 28 to 46%, and most desirably Fixed carbon 49 to 71%, and mostdesirably Ash 1 to 15%, preferably l to 5%,

and most desirably 3 to 4%.

While most of the raw material for the present invention would bedescribed as bituminous coal, it is intended also to include in thisdesignation semi-bituminous and subbituminous coals which can be usedand have the above properties.

PULVERIZING An important aspect of the present invention is theincorporating into the coal prior to reaction under heat of potentialchemical energy capability by shattering the macro molecules, andforming free valences. In order to do this, it is not enough merely togrind by' any one of the accepted methods which will produce nelydivided coal particles. It is necessary to shatter the particles byimpact.

The most effective way of accomplishing this is by passing the particlesthrough a vertical or horizontal Raymond mill, of well known characterin the art, which subjects the particles of bituminous coal to impactand reduces them to very fine size.

A Raymond mill useful in pulverizing the bituminous coal according tothe invention is illustrated in Crites U.S. Patent No. 2,561,564,granted July 24, 1951, for Pulverizing Mill Separator, Having Whizzerand Directional Blades and Combustion Engineering, Inc., RaymondDivision, Bulletin 78 (1955). In this mechanism as well shown in thedrawings of this patent, bituminous coal enters near the bottom andencounters pivoted hammers 27 which impact against it. Finely dividedparticles are then accelerated by whizzer blades 11 and finely dividedmaterial is withdrawn from the mill by suction applied by fan 12 at thetop.

It will be evident that in the Raymond mill air is circulated throughthe mill and it cools the particles notwithstanding that much heat isgenerated by the impact and keeps the particles from compacting into amass and also lblows the ground products out of the mill.

The neness of the etiluent from the impact grinding should be at least60% by weight through 200 mesh per linear inch and at least 25% ybyweight through 325 mesh per linear inch, preferably at least by weightthrough 200 mesh per linear inch, and at least 60% by weight through 325mesh per linear inch.

Bright banded bituminous coai reduced to this fineness under impactpulverizing has the macromolecules disrupted, has a large amount of freevalence and will ow like a plastic under molding as later described.

Screen analysis of two products which have been used in an experimentalprogram in accordance with the present invention are as follows:

Screen size Product A Product B Nothing on Nothing on 5% on Nothing on5% 0n 4% on 9% on 7% on 55% on 20% on 325 mesh 30% through 69% throughADDITIVES An important aspect of the invention is the creation ofcontrollable pores in activated carbon before it is first activated. Inthe process of the invention, it will, of course, be evident thatmoisture is evolved by the coal during heat treatment both because aslater explained moisture is deliberately retained or added to the coal,and also because in the pyrolitic decomposition which the coal undergoesduring heat treatment, considerable moisture is evolved from hydrogenand oxygen or hydroxyl present in the coal and in some cases in theadditive. The evolution of the moisture present as such is not helpfulin producing pores, but the evolution of the water formed by pyroliticdecomposition of the coal and particularly the formation of freevalences by its evolution is helpful in producing pores which are usefulin the activated carbon.

Also, in the pyrolytic decomposition of bituminous coal many volatilecomponents are given off and others similar are evolved when tar isincorporated as a binder. However I find that this also is not desirablein producing an effective pore structure in the final activated carbon.

It appears that the most desirable activated carbon is the result ofspecial additives which have a combination of the following features:

(1) Size of molecule which apparently controls the minimum space vacatedby the additive in pyrolytically decomposing or distilling.

(2) Volatiles of the additive which may be expressed in terms of itsvapor pressure and boiling point.

(3) Ability of the additive to combine with the coal, especially withits free valences, and form a surface chemistry condition adjoining thepore which is favorable to adsorption.

(4) Capability of the additive to cooperate with the products evolved bythe coal in promoting azeotropic boiling which is favorable to flush outthe pores.

(5) Critical size of the pore influenced by all these factors whichdetermines whether it is in effect a micropore, a submicropore or amacropore. It will be evident that the size of the pore not onlycontrols the ratio of weight to surface area of the activated carbon butalso influences the ability of the activated carbon to adsorb componentsfrom either a liquid or a gaseous phase.

EXOTHERMIC REACTIONS WITH ADDITIVES An unusual feature of the presentinvention is that after pulverizing the coal under impact to causeformation of free valences, certain of the additives incorporated withthe finely divided coal, preferably prior to but permissi- 'bly afterpulverizing (assuming the additives are about as nely divided as thecoal) will under heat treatment producey exothermic reactions which areremarkably effective in producing a superior activated carbon at lowcost.

vOne' class of very desirable additives is cereals, seeds or beans,hereinafter called cereals, including lbran, white corn meal, yellowcorn meal, or soyabean flour (low fat). These cereals contain asubstantial quantity of phosphorus. For example, the phosphorus contentsof these materials in milligrams per hundred grams are as follows:

Bran 1215 Corn meal 248 Soyabean flour (low fat) 623 ously been used inactivated carbon, for example, magnesium oxide, magnesite, dolomite,calcite, or tricalcium phosphate.

The concentration of cereal such as bran or the like is 1 to 10% on thedry weight of the coal, preferably 2 to 7%, and most desirably 2 to 3%.The concentration of the magnesium oxide or other basic component isalso in the range of 1 to 10%, and preferably 2 to 7%, on the dry weightof the coal, and most desirably about 2 to 3%.

Experience indicates that fiber and carbohydrate in these cereals havethe property of associating themselves with very small (micron size)coal particles which are likely to contain the greatest number of freeValences per unit of weight. When subjected to high pressure as laterdiscussed, they produce macromolecules with a high density of crosslinking, whereas the coal itself originally had a rather low density ofcross linking. After high pressure molding there is a tendency to form amaterial which is like a plastic from the standpoint of strength andother properties.

Activated carbon when made from one of these cereal components,particularly when incorporating an alkaline material such as magnesia,is very suitable as a brightening and buffering agent in treating sugarrefining solutions, dextrose, Syrups and vegetable oils. The magnesia orthe like after activating of the carbon tends to prevent the inversionof can sugar. Activated carbon of this type is also very useful forpurifying citric acid, malic acid, pharmaceutical materials and water,especially for use in power plants. It is also incorporated in side walltires to prevent bleeding.

It has a pore diameter between 2 and 45| A. units.

The property of reacting exothermically wih coal is also possessed byaldehydes which have boiling points in the range between 220 and 800 F.The preferred aldehydes for this purpose are furfural, benzaldehyde andparaldehyde.

The concentration of aldehyde used is 1 to 10% on the dry weight of thecoal and preferably 2 to 7%, most desirably 2 to 3%.

My tests indicate that 2% furfural on the dry weight of the coalproduces after heat treatment pores of about 6 A. units. The aldehydecondenses with hydroxyl groups in the coal during heat treatment whenthe temperature rises to about 300 F. and produces a high densitynetwork of macromolecules.

Activated carbon of this type is very good for catalyst carriers, forexample, employing platinum black, and for adsorbing toxic gases in gasmasks and in mines, for solvent recovery, for air conditioning filters,and for purifying tobacco.

A third group of additives which react exothermically with coal duringheat treatment are the amines and ammonium salts which boil or decomposebetween 220 and 800 F. Suitable amines are urea, ammonium oxalate,monoethanol amine, diethanol amine and triethanol amine. Suitableammonium compounds are ammonium chloride, ammonium fluoride and ammoniumbifluoride. These activated carbons are especially good for gasadsorption, particularly of acid gases such as carbon dioxide, sulphurdioxide and hydrogen sulphide. They are very effective for airconditioning filters and for purifying electroplating solutions.

The activated carbon produced using amonium chloride evolves products ofdecomposition during heat treatment at temperatures above about 550 F.It produces an activated carbon having a very large number of micro andsubmicropores in the range of 3 to 4 A. units. This activated carbon isslightly acid and is especially suitable for adsorbing alkaloids, aminoacids, such as glutomic acid, for purifying glycerine and for purifyingelectroplating solutions.

Activated carbon which incorporated 2% of urea on the dry weight of thecoal added in aqueous solution was found to give a superior gasadsorbing activated carbon.

7 SWELLING AND AZEOTROPIC BOILING All of these additives now to bereferred to are employed in concentrations of 1 to 10%, preferably 2 to7%, and most desirably 2 to 3%, on the dry weight of the coal.

There are a number of different additives which attack the humins in thecoal and tend to promote swelling of the coal.

Alcohols (and phenols) having boiling points in the range from 220 to800 F. tend to exert swelling action on the coal, thus promotingformation of pores, and are very effective in producing a flushingaction which clears out the pores very effectively and makes anunusually active carbon. The preferred alcohols are glycerol, propyleneglycol, and normal hexanol. The preferred phenols are phenol, cresol,catechol and resorcinol.

The activated carbon made with these alcohols and phenols as additivesis rather similar to that obtained from bran, corn meal or soyabean our.

Hydrocarbons having, 2 or 3 fused rings, such as naphthalene, anthraceneand 1,2,3,4-tetrahydronaphthalene when used as additives produceactivated carbon having micropores, which is especialy effective ina-dsorbing polymers of high molecular Weight from solution.

Esters of straight fatty chain acids, boiling between 220 and 800 F.,such as butyl acetate and amyl acetate, produce activated carbons havingintermediate pore sizes between 6 and 7 A. units, which are veryeffective in adsorbing materials of this size range from liquids andgases.

Ketones boiling between 220 F. and 800 F. such as methylethylketone andmethylisobutylketone produce activated carbon having properties similarto the alcohols and having the azeotropic boiling tendency.

For adsorbing halides from liquids and gases, an especially effectiveactivated carbon can be made by incorporating as an additive achlorinated hydrocarbon boiling between 220 and 800 F., such astetrachloroethylene or perchloroethylene. These produce pores having aparticle size of about 1l A. units.

Activated car-bon made in this way is especially effective for adsorbinghalide solvent vapors, and gases containing halides such as arsenictrichloride and phosphorus pentachloride.

Another Very effective additive is oxalic acid in concentrations of 1 to10% on the dry weight of the coal, preferably 2 to 7%, and mostdesirably about 2 to 3%. Oxalic acid produces a very effective acidicactivated carbon having pore size of about 4.25 A. units.

In all of the above additives the concentration will be between about 1and 10% on the dry weight of the coal, preferably 2 to 7%, and mostdesirably about 2 to 3%. All of the above additives can be put in priorto pulverizing and in the case of the dry additives, are preferablyadded at this time. The liquid additives, however, are preferablyincorporated after pulverizing.

In general the invention permits an activated carbon having a selectedpore size and selected surface chemistry capable of adsorbing materialswhose particle size and whose properties are known.

ADJUSTMENT OF MOISTURE Regardless of the character of the additive orthe question of whether it is a liquid or solid, it is important toregulate the moisture content of the coal to bring it within a range of2.5% to 11% on the dry weight of the coal, preferably A moisture contentof 21/2% is enough lfor best results in the case of the coarser coals,but for best results with the finer coals, the moisture content prior tomolding should be in the range from 7 to 11%.

The moisture performs three different functions. It acts as a lubricantto make the coal particles flow plastically under the molding pressure.It tends to hold the very ne coal particles in uniform distributionthroughout the briquette. It seals the mold against tendency to extrudecoal particles between the punch and the die in the closed mold. Themoisture adjustment is preferably made in a blender.

8 MOLDING Molding must be carried out in a closed chamber mold. An augerpress should not be used.

While molding may be carried on in a closed chamber brick molding press,it is preferred to use a tableting press such as a Stokes DD2 Press (15tons), having a die size of 1%6 inches X 1/2 inch. When molding at10,000 p.s.i., the tablets obtained in the present invention have adensity of about 1.05 grams per cubic centimeter. Under 11,000 p.s.i.,the density of the tablets is 1.10 grams per cubic centimeter. Whenmolding at 13,000 p.s.i., the density is 1.15 grams per cubiccentimeter. When molding at 20,000 p.s.i, the density is grams per cubiccentimeter In general, the density increases with the molding pressure.

When molding high volatile coals having a volatile content of 38% byWeight or higher, the molding pressure can be as low as 5000 p.s.i., orwhen molding coals having lower volatility (below 38% by weight), vthemolding pressure should be at least 10,000 p.s.i., and preferably atleast 11,000 p.s.i. Pressures up to 30,000 p.s.i. are desirable, andhigher pressures can be used but are not regarded as beneficial.

The briquette or tablet after molding resembles many plastic moldings.It has a brittle fracture like chinaware.

GRANULATION The tablets or briquettes are preferably next broken down toa size in the range between A inch and 1;/18 inch'. While thisgranulation can be accomplished before heat treatment, it can be doneafter heat treatment. The preferred mechanism for granulation is aCrusher which will produce brittle fractures, for example, a CumberlandCrusher, in which the granulation is accomplished by saw blades.

HEAT TREATMENT The coal after molding and before or after granulation isheat treated at a temperature between 250 and 800 F. and not in excessof the temperature of agglomeration for a time of at least four hoursand preferably -four and one-quarter hours.

It is definitely not desired to have the coal agglomerate or fuse duringheat treatment and, therefore, while the coal still is plastic, it mustnot be heated high enough to agglomerate. The test used is to heat treatat a succession of different temperatures and then transfer the heattreated coal samples to a muiile furnace heated at 1742 F. (950 C.) andleave it there for seven minutes. If a fused mass forms under this test,it means that the heat treatment had previously caused the coal toagglomerate, and the heat treating temperature was too high.

The heat treatment is preferably carried out in a multiple hearthfurnace such as Herreshoff Furnace (Nichols Engineering and ResearchCorporation, New York City) in which initially gas flames'heat thedifferent hearths, and where the reaction is exothermic, in the case ofbran, corn meal, soyabean flour, aldehyde, amine or ammonium compoundsas the additive, the flames can be cut off once the exothermic reactionstarts. Suitable temperatures forheating the various hearths in aparticular case are as follows:

It should be mentioned that the additive yperforms a very importantlfunction in accelerating the operation as well as producing a muchbetter product. For example, to heat treat the coal even much lesseffectively without an additive would require at least nine hours.

F. Corn meal 800 Furfural 600 Urea 700 Ammonium chloride 700Tetrachloroethylene 700 Heat treatment in accordance with the inventiondrives olf a great deal of water vapor, which evidently comes fromhydrogen combined with the coal long after any uncombined moisture hasceased to come off, and there is very little loss of carbon in the heattreatment of the coal.

ACTIVATION Activation of the coal according to the present invention andreactivation follow well-accepted present practice, that is, heating toan elevated temperature in the presence of steam to form water gas. Theactivation and reactivation temperatures will be between 11l2 F. (600C.) and 1832 F. (1000 C.), and preferably between 1742 F. (950 C.) and1778 F. (970 C.). Temperatures for activation higher than 1832 F. arenot recommended, and if submicropores are to be retained, activationshould be carried on at lower ternperatures. Reactivation at highertemperatures is likely to form more macropores.

The activated carbon of the invention weighs about 35 pounds per cubicfoot at a density of 1.20 grams per cubic centimeter and 34 pounds percubic foot at a density of 1.15 grams per cubic centimeter.

Example 1 Following the general technique described above, bright bandedbituminous coal having the following analysis by weight was used:

Two different products were pulverized in the Raymond Single-PassVertical Mill, one having the particle size of Product A described andthe other having the particle size of Product B above described. Priorto pulverizing, of bran and 5% of magnesium oxide, both on the dryweight of the coal, were incorporated. The products were molded at10,000 p.s.i., 11,000 p.s.i., 13,000 p.s.i. and 20,000 p.s.i., obtainingdensities as above set forth, and the product was heat treated for fourhours at a maximum temperature of 800 F. Very superior sugar carbonswere obtained, as above set forth.

The products molded using the ner grain size distribution (product B)had lower molecular weights and more reactive free valences than theproducts using the coarser particle size (product A).

The activated carbon produced in Example 1 was compared for adsorbenceof coloring material in molasses with a standard commercial activatedcarbon, using the well known absorbence test. Forty milliliters ofmolasses (Brer Rabbit) was dissolved in 1000 cc. of distilled water,suitably bulered. To cc. samples of this molasses solution was added inone case 100 mg. of the control commercial activated carbon and inanother case 100 mg. of the activated carbon of Example 1, and eachsample was boiled for seconds. The samples were ltered hot throughWhatman lter paper and tested comparatively in the same colorimeter. Themolasses solution alone gave a light transmittance of 48.5. The sampletreated with commercial activated carbon gave a light transmittance of67.5, the increase being 19.0. The molasses sample treated with theactivated carbon of the invention gave a light transmittance of 89.0, oran increase of 40.5, or was more than twice as eiective as the control.

Example 2 The procedure of Example 1 was repeated except that 5% ofyellow corn meal on the weight of the dry coal was used instead of 5% ofbran. Comparable products were obtained.

Example 3 The procedure of Example 1 was repeated, using 5% of soyabeanour (low fat) on the weight of the dry coal rather than bran. Theresults were comparable.

Example 4 The procedure of Example 1 was repeated, using 2% of furfuralon the weight of the dry coal rather than bran and magnesia. The heattreatment was carried on at a maximum temperature of 600 F. Theactivated carbon has micropores of about 6 A. units in diameter and wasvery eiective for adsorbing toxic gases and solvents.

A comparison of light transmittance was made according to the testreferred to in Example 1. The light transmittance of the molassestreated with this activated carbon was 78.5 with an improvement of 30,as compared with an improvement of 19 for the activated carbon control,or a benet of about 50%.

Example 5 The procedure of Example 1 was carried out, using 2% of ureaon the dry weight of the coal instead of bran and magnesia.

The heat treatment was carried out at a maximum temperature of 700 F. Avery effective gas adsorbent activated carbon was obtained.

Example 6 The procedure of Example 1 was carried out, omitting the branand magnesia and using 2% of ammonium chloride on the weight of the drycoal, the ammonium chloride being added as an aqueous solution after thecoal was pulverized. The heat treatment was carried out at a maximumtemperature of 700 F. The coal began to gasify at 550 F. A very largevolume of micro and submicropores of about 3 to 4 A. unit diameter wasproduced. The activated carbon was superior for adsorbing alkalinematerial such as amino acids.

Example 7 The procedure of Example 1 was carried out, substif tuting 2%of tetrachloroethylene on the dry weight of the coal for the bran andmagnesia. The pores produced were of a diameter of 11 A. units andlarger. The activated carbon was very elfective for adsorbingchlorinated or other halogenated solvents.

Example 8 The procedure of Example 1 was carried out, substituting 2% ofoxalic acid on the dry weight of the coal and omitting the bran andmagnesia. The activated carbon produced was acidic and had a pore sizeof about 4.25 A. units.

APPARATUS The apparatus shown in FIGURE 1 takes coal from a storage bin20 and passes it through a bar screen 21, where it is picked up by a`feeder 22 and passed through a crusher 23 to a scalping screen 24 fromwhich the coal is passed by a feeder 25 to an elevator 26 whichdischarges to a storage bin 27 and a feeder 28. The feeder 28 emptiesinto a single pass vertical Raymond impact pulverizer 30 having aircirculation provided at 31 and feeding to an air classifier 32.Excessively large particles are recirculated at 32', and particles ofsuitable neness are carried in an air stream 33, which communicates witha classifier 34, which feeds the main stream of effluent in a feeder 35and consolidates coal particles recovered by a rotary precipitator 36,returning coal to the feeder at 37 and discharging air to the atmosphereat 38. Finely divided coal is carried by an elevator 40 to a storage bin41, which also receives coal returned in a stream 42 from a dustcollector. A feeder 43 progresses the coal and mixes with it an additive44 (assuming that the additive is to be put in after the impactpulverizing), and any required moisture. The feeder empties the mixtureof coal and additive or additives into a briquetting press 45 having aclosed mold. Briquettes are discharged into a feeder 46, which conveysthem to a crusher 47, which may if desired be supplemented by a grinder48. The particles are picked up by an elevator S and discharged into astorage bin S1 and then to a feeder 52 and a classifying screen 53.Oversize particles are returned by a ow line 54 to the grinder, and fineparticles that should be recycled are recycled by means not shown.Particles of coal leave this operation at 55.

FIGURE 2, which shows the heat treatment, receives molded coal particlesat 56 to enter an elevator 57 to discharge to a storage bin S and thenby a weighing scale feeder 60 to enter a heat treating furnace 61suitably of the multiple hearth type. The heat treating furnace 61discharges heat-treated coal granules through a cooler 61 to an elevator62 and then to storage bin 63. At the top of the heat treating furnace61 there is a dust collector 64 discharging gas and vapor to atmosphereat 65 and discharging particles to a storage bin at 66. The heattreating furnace has internal gas burners on each hearth, which may becut off once the reaction is started if the reaction is exothermic.Means for introducing steam at 67 is shown for emergency use ifnecessary to cool the heat treating furnace.

The heat-treated carbon from the storage bin 63 passes through a weightscale feeder 68 to a multihearth activating furnace 70, from which theproduct discharges to a cooler 71. Steam for the activation reaction isintroduced at 72, and vapor and dust passes through dust collector 73,discharging the vapor to atmosphere at 74 and returning any particlescollected by the dust collector through a line 75 to a storage bin. Theactivation furnace has internal gas burners not shown. The activationtemperature will be between 600 C. and 1000 C., as previously mentioned.In some cases the activation can be carried on without introducing steamsince the presence of controlled amounts of carbon dioxide and carbonmonoxide in the combustion gases will accomplish activation withoutrequiring introduction of steam, as well known in the art.

The finished product is suitably further pulverized if required,classified as to size and stored, preparing for shipment.

Having thus described my invention what I claim as new and desire tosecure by Letters Patent is:

1. A process of making activated carbon, which comprises pulverizingbright banded bituminous coal under impact in the presence of a streamof air until the particles are of the following size range:

at least 60% by weight through 200 mesh, at least 25% by weight through325 mesh,

introducing into the finely divided coal between I and by Weight of thedry coal of a cereal which will break down at a temperature between 220F. and the temperature of heat treating, regulating the moisture contentof the finely divided coal to between 2.5 and 11% on the dry Weight ofthe coal, molding the finely divided coal into briquettes in a closedmold under a pressure as follows: where the volatile in the coal isabove 38% by weight,

in excess of 5 000 p.s.i., where the volatile in the coal is below 38%by weight,

in excess of 10,000 p.s.i., 4heat treating the coal in thus molded format a temperature between 2509 F. and 800 F. and not in excess of thetemperature of aglomeration of the coal for a time of at least fourhours, the coal and the cereal reacting exothermically during heattreatment, breaking down the briquettes into granules, and activatingthe carbon granules.

2. A process of claim 1, in which the quantity of additive is between 2and 3 3. A process of claim 1, in which the coal is pulverized in aRaymond mill.

4. A process of claim 1, in which the coal after pulverizing has thefollowing size range:

atleast by weight through 200 mesh,

at least 60% by weight through 325 mesh.

5. A process of claim 1, in which the coal has the following analysis byweight:

volatile between 28 and 46%. fixed carbon between 49 and 71%. ashbetween 1 and 15%.

6. A process of claim 5, in which the coal has an ash content between 1and 5% by weight.

7. A process of claim 5, in which the coal has the following analysis byweight:

volatile between 39 and 42%. fixed carbon between 54 and 58%. ashbetween 3 and 4%.

8. A process of claim 7, in which the moisture content is regulated tobetween 7 and 11% on the dry weight of the coal.

9. A process of making activated carbon, which comprises pulverizingbright banded bituminous coal under impact in the presence of a streamof air until the particles are of the following size range:

at least 60% by weight through 200 mesh,

at least 25% by weight through 325 mesh, introducing into the finelydivided coal between l and 10% by weight of the dry coal of an organicadditive of the class consisting of furfural, urea, oxalic acid,glycerol, propylene glycol, normal hexanol, phenol, cresol, resorcinol,butyl acetate, amyl acetate, methylethylketone and methylisobutylketone,regulating the moisture content of the tinely divided coal to between2.5 and 11% on the dry weight of the coal, molding the finely dividedcoal into briquettes in a closed mold under a pressure as follows:

where the volatile in the coal is above 38% by weight,

in excess of 5000 p.s.i., where the volatile in the coal is below 38% byweight,

in excess of 10,000 p.s.i., heat treating the coal in the thus moldedform at a temperature between 250 F. and an upper limit as follows:

furfural 600 oxalic acid 700 all other additives not in excess of thetemperature of agglomeration of the coal for a time of at least fourhours, breaking down the briquettes into granules, and activating thecarbon granules.

10. A process of claim 9, in which the coal has the following analysisby weight:

volatile between 28 and 46% fixed carbon between 49 and 71% ash between1 and 15% 11. A process of claim 10, in which the coal has an ashcontent of between 1 and 5% by weight.

12. A process of claim 9, in which the coal has the following analysisby weight:

volatile between 39 and 42% fixed carbon between 54 and 58% ash between3 and 4% 13. A process of claim 12, in which the moisture content isregulated to between 7 and 11% on the dry welght of the coal.

13 14. The process of claim 9, in which the quantity of 1,768,963additive is between 2 and 3% by Weight. 2,944,031 15. A process of claim9, in which the coal after pul- 1,729,162 verizing has the followingsize range: 2,008,144 atleast 85% by weight through 200 mesh, 2,008,145

at least 60% by weight through 325 mesh. 5

References Cited UNITED STATES PATENTS 2,624,712 1/1953 Donegan 252-42110 2,915,370 12/1959 Mitchell 23-209.1 2,304,351 12/1942 Goss 202-9ODell 252-421 Mason 252-421 Coates l252-421 Morrell 252-421 Morrell252-421 DANIEL E. WYMAN, Primary Examiner P. E. KONOPKA, AssistantExaminer U.S. C1. X.R.

